Burglary, aimed at the theft of property from both commercial and private premises, whether these be movable road vehicles such as trucks, vans, recreational vehicles, trailers, and the like, or stationary structures such as stores, warehouses, garages, barns, and the like, is an ever growing problem in our society. Even the development of sophisticated anti-theft devices such as burglar alarms (with or without a direct link to a police station or a private protective company central office) and special pickproof locks, as well as the development of high-quality conventional padlocks and hasps, has not stemmed the tide, because the sophistication of the burglars has advanced commensurately. Frequently, it takes a professional thief less than a minute to overcome any of the currently available anti-theft devices, even if that requires sawing or cutting through the shackle or bolt of a padlock or the staple of a hasp. By and large, of course, speed and silence in neutralizing an anti-theft device and entering the protected premises are the principal desiderata for a burglar, because they lessen the chances of his or her being detected and apprehended.
Numerous attempts have been made over the years to provide guards for conventional padlocks. Representative of the more recent of these are the guards shown in U.S. Pat. Nos. 3,392,555 (Beaver 1968); 3,884,057 (Maurer 1975); 4,033,155 (De Lucia 1977); 4,322,102 (Lindblom 1982); 4,380,160 (Hoffman 1983); 4,535,612 (Seremet 1985); 4,843,845 (Poe 1989); 4,852,920 (DeForrest, Sr. 1989); and 4,866,960 (Brower 1989). The principal aim of these and other lock guard devices has been to make it more difficult and hence time-consuming for a burglar to gain access to the lock for the purpose of cutting either the bolt or shackle of the lock or the staple of an associated hasp with a bolt cutter or for sawing through such a shackle or staple with a hacksaw. Nevertheless, to the best of my knowledge the known lock guards have not become universally accepted; quite to the contrary, an inspection of any random number of padlocked store fronts and truck or van doors reveals that in almost all so-protected premises a standard padlock is used without an associated guard structure, the only feature being relied on for increasing the difficulty of destruction of the lock by means of a hacksaw or a bolt cutters being the increase in the size of the lock and in particular in the thickness of the bolt or shackle of the padlock and/or of the staple of the hasp.
One particular non-conventional type of padlock which was originally invented for use in protecting the cabinets of coin-operated vending machines is the cylindrical lock disclosed in U.S. Pat. No. 3,769,821 (Randel 1973). This type of lock has a flat-faced cylindrical housing which is partially traversed substantially axially thereof by a slot-shaped channel extending inwardly from one of the flat faces of the housing, the channel being adapted to receive a pair of apertured flanges supported by co-operating parts of the closure of the cabinet and arranged to have their respective apertures in registry with one another when the cabinet is closed. Internally, the housing of the lock is further partially traversed by a diametrical passageway which extends from the circular wall of the housing and perpendicularly intersects the channel. Slidably disposed for both rotary and axial movement in the passageway is a key cylinder which at its innermost end carries a straight rod or bolt. The arrangement is such that the bolt is protracted across the channel when the key cylinder is pushed into the housing and into its locked position, and that the bolt is retracted from the channel when the cylinder is released by the key and shifted outwardly of the housing to its unlocked position. When the cabinet is closed, the two flanges are in back to back abutting relation with each other and have a combined thickness just a little less than the height of the channel in the lock housing. As a consequence, the lock can be slid axially onto the flanges by fitting the channel over them until the lock is fully seated thereon. Since at that point the registered apertures of the two flanges are aligned with the bolt, the latter can be axially protracted through the apertures in the flanges and locked in place by the key cylinder, thereby to secure the lock to the flanges.
The principal difference between the Randel lock and the conventional padlocks was, of course, the fact that it did not have the usual U-shaped link or shackle, i.e., that it had no exposed element which could be rapidly and relatively easily cut through by a bolt cutter or sawed through by a hacksaw. This was certainly an advantage of sufficient magnitude that, one would think, ought to have more than justified the somewhat higher cost of the Randel lock. Nevertheless, the commercial preeminence of conventional padlocks in the marketplace has remained substantially unimpaired, quite possibly (although the reason may be somewhat more complicated) because the Randel lock is actually not invulnerable to a skilled and determined burglar in at least one respect by virtue of the construction of the lock and the flanges. Thus, when the lock, in use, is mounted on and secured to the flanges of the closure components of a cabinet or comparable protected structure, the back flat face of the lock housing is invariably spaced somewhat from the thereto juxtaposed faces of the respective base members of the two flanges by which the latter are secured to the cabinet or other structure being protected. This enables either the prying end of a crowbar or the blade of a hacksaw to be inserted into the space behind the lock for either breaking the lock off the flanges by brute force or sawing through the flanges on which the lock sits.